Katie Stallard

Asia Correspondent

South Korea has convened its national security council, but there is no panic on the streets of Seoul.

Thirty-five miles from the North Korean border, and the thousands of artillery pieces stationed there, there is no sense that conflict is about to break out.

Maybe that's borne of living with the threat for decades, in a country that is still technically at war, with a truce, not a peace treaty in place with the North since the suspension of hostilities in 1953.

Video:US-North Korea tensions rise

But more likely it's because the prospect of US military action to "solve" what Donald Trump describes as the "menace" of North Korea, no matter how tough that sounds, would have such devastating consequences as to render it all but unthinkable.

An attack on North Korea would not go the way of recent US strikes on Syria and Afghanistan.

No matter how calibrated, how supposedly surgical the strike, North Korea would retaliate - they can't reach the US mainland, yet, but they can hit South Korea and Japan, both American allies, with missiles and conventional artillery.

Image:A parade in Pyongyang on Saturday

Millions of civilians, and tens of thousands of US military personnel would be within range of the response.

Which is why successive US presidents have weighed and declined to authorise military action.

This is not a new problem. President Nixon wrestled with it back in 1969, when North Korea shot down a US spy plane, killing all 31 on board.

Video:China warning as pressure over N Korea rises

The risk of triggering all-out war was such that in the end he settled for a brief show of force at sea.

The options have not improved greatly in the nearly five decades since, only now North Korea has nuclear and chemical weapons too.

And so the cycle continues - all the while North Korea's weapons and nuclear programmes advancing.

Kim Jong-Un is determined to pursue nuclear weapons - it's part of his signature ruling policy - and the difference, he believes, between survival and ending up like Muammar Gaddafi or Saddam Hussein.

Image:Missiles at a parade in Pyongyang, North Korea

Mr Trump is equally determined that won't happen, that the United States will not tolerate a nuclear-armed North Korea.

Something is going to have to give.

And for all of the impressive pictures of the "powerful armada" President Trump has diverted to the peninsula, the reality is likely to come down to a combination of economic pressure and negotiation.